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<head><meta charset="utf-8"><title>Miri test failures · t-compiler/wg-mir-opt · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/index.html">t-compiler/wg-mir-opt</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html">Miri test failures</a></h3>

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<a name="201577772"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201577772" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201577772">(Jun 22 2020 at 08:11)</a>:</h4>
<p>Uh-oh, I think we have an incorrect optimization somewhere... the Miri test suite started failing with <code>-Zmir-opt-level=3</code>: <a href="https://travis-ci.com/github/rust-lang/miri/jobs/352020194">https://travis-ci.com/github/rust-lang/miri/jobs/352020194</a></p>



<a name="201578753"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201578753" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201578753">(Jun 22 2020 at 08:22)</a>:</h4>
<p>specifically, <a href="https://github.com/rust-lang/miri/blob/31ad5f6b2b93f78d3366c0654609f4b685043ec9/tests/run-pass/union.rs#L21">this assertion fails</a></p>



<a name="201580111"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201580111" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> oli <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201580111">(Jun 22 2020 at 08:40)</a>:</h4>
<p>yea, mir opt level 3 contains buggy things</p>



<a name="201580159"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201580159" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> oli <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201580159">(Jun 22 2020 at 08:41)</a>:</h4>
<p><a href="https://github.com/rust-lang/rust/pull/73262">https://github.com/rust-lang/rust/pull/73262</a> is an example</p>



<a name="201583533"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201583533" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201583533">(Jun 22 2020 at 09:24)</a>:</h4>
<p><a href="https://github.com/rust-lang/rust/issues/73609">https://github.com/rust-lang/rust/issues/73609</a></p>



<a name="201583539"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201583539" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201583539">(Jun 22 2020 at 09:25)</a>:</h4>
<p>well this is a regression, it worked before</p>



<a name="201583788"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201583788" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201583788">(Jun 22 2020 at 09:27)</a>:</h4>
<p><span class="user-mention silent" data-user-id="124288">oli</span> <a href="#narrow/stream/189540-t-compiler.2Fwg-mir-opt/topic/Miri.20test.20failures/near/201580159">said</a>:</p>
<blockquote>
<p><a href="https://github.com/rust-lang/rust/pull/73262">https://github.com/rust-lang/rust/pull/73262</a> is an example</p>
</blockquote>
<p>wait we are keeping <em>known incorrect</em> optimization passes enabled?!? that's like a deliberate soundness issue, why are we doing this?^^</p>



<a name="201583816"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201583816" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201583816">(Jun 22 2020 at 09:27)</a>:</h4>
<p>"high opt level" shouldn't imply "contains critical bugs", that just makes no sense...</p>



<a name="201584314"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201584314" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201584314">(Jun 22 2020 at 09:33)</a>:</h4>
<p>if for some reason you want to keep those broken optimizations reachable, please hide them behind <code>-Zmir-please-break-my-code</code> or so</p>



<a name="201584456"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201584456" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> oli <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201584456">(Jun 22 2020 at 09:35)</a>:</h4>
<p>yes, we discussed that recently and it will come</p>



<a name="201584636"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201584636" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201584636">(Jun 22 2020 at 09:37)</a>:</h4>
<p>:)</p>



<a name="201584695"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201584695" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201584695">(Jun 22 2020 at 09:38)</a>:</h4>
<p>I'll make miri test mir-opt-level=2 until then</p>



<a name="201585888"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201585888" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201585888">(Jun 22 2020 at 09:44)</a>:</h4>
<p>oh no I have to go all the way down to 1...</p>



<a name="201586046"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201586046" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Jonas Schievink  [he/him] <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201586046">(Jun 22 2020 at 09:45)</a>:</h4>
<p>Does the const prop change even touch opt-level=3-only code? Maybe it miscompiles on all levels, but you only notice on levels 2 and up</p>



<a name="201586367"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201586367" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> bjorn3 <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201586367">(Jun 22 2020 at 09:48)</a>:</h4>
<p><code>Operand::Indirect</code> only gets const-prop'ed at <code>mir-opt-level=2</code> and higher: <a href="https://github.com/wesleywiser/rust/blob/2f49d554ff1afd1633a01d6b84192ad0147d9097/src/librustc_mir/transform/const_prop.rs#L705-L709">https://github.com/wesleywiser/rust/blob/2f49d554ff1afd1633a01d6b84192ad0147d9097/src/librustc_mir/transform/const_prop.rs#L705-L709</a></p>



<a name="201586372"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201586372" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201586372">(Jun 22 2020 at 09:48)</a>:</h4>
<p>the new thing is actually a stable-to-nightly regression:<br>
<a href="https://github.com/rust-lang/rust/issues/73609#issuecomment-647409694">https://github.com/rust-lang/rust/issues/73609#issuecomment-647409694</a></p>



<a name="201586851"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201586851" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201586851">(Jun 22 2020 at 09:53)</a>:</h4>
<p>and it has nothing to do with unions... it seems to just ignore mutation via references entirely <span aria-label="scared" class="emoji emoji-1f628" role="img" title="scared">:scared:</span></p>



<a name="201587013"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/189540-t-compiler/wg-mir-opt/topic/Miri%20test%20failures/near/201587013" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> RalfJ <a href="https://rust-lang.github.io/zulip_archive/stream/189540-t-compiler/wg-mir-opt/topic/Miri.20test.20failures.html#201587013">(Jun 22 2020 at 09:54)</a>:</h4>
<p>how does this not break, like, <em>everything</em>?^^</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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